The invention relates to a magnetooptical recording element. The recording element comprises a substrate and a thin recording layer provided thereon. The recording lazer is an alloy of a rare earth metal, a transition metal and boron. The alloy has an intrinsic uniaxial magnetic anisotropy and an easy axis of magnetization which is perpendicular to or substantially perpendicular to the plane of the layer.
Such an optical recording element is known from Netherlands Patent Application No. 7900921 (corresponding to U.S. Pat. No. 4,310,899).
In the known recording element an amorphous recording layer is used which comprises a comparatively high content of 15-30 at.% of the element boron. The content of the transition metal, in particular Fe, is approximately 50-70 at.%. The rare earth metal, in particular Gd, is present in a quantity of 14-26 at.%.
According to Netherlands Patent Application No. 7900921, the addition of boron has the advantage that the alloy crystallizes at a higher temperature above the Curie temperature. The stability of the recording layer is thereby enhanced. Notably, the recording layer has a greater resistance to irreversible structural changes which change the magnetic properties of the layer.
Although this advantage enables the practical usability of the recording element, it should be borne in mind that an amorphous layer by nature is an unstable layer. When high requirements are imposed upon stability for a long period in use, the known element is not satisfactory. In the long run structural changes occur in the known amorphous layer, in particular as a result of the ever recurring local heating to the Curie temperature.
Another disadvantage is that the amorphous layer of the known recording element is rather sensitive to oxidation. This also adversely influences the life of the element.